Performance of six influenza rapid tests in detecting human influenza in clinical specimens
Introduction
Influenza is a respiratory infection that can result in significant morbidity and mortality, particularly in the young, elderly or immunosuppressed (Simonsen, 1999). However, rapid diagnosis of influenza infection can facilitate the use of appropriate treatment, both improving the patients clinical outcome and significantly reducing hospital costs (Bonner et al., 2003). A large number of rapid influenza detection tests are now available that are simple to use, quick (generate a result in 15 min) and can be performed outside the laboratory. In general, previous studies have reported the tests to have a good specificity (99–100%), however different studies have reported significantly different sensitivity values even when evaluating the same test (Storch, 2003). For example the reported influenza A sensitivity for the Becton Dickinson Directigen Flu A + B Test ranges from 44% (Cazacu et al., 2004) to 96% (Chan et al., 2002). While study-to-study variability in sensitivity with the same test can be explained by the differences in specimen type, influenza type/subtype circulating, patient age and the ‘gold standard’ test used for comparison, these differences highlight the difficulties in comparing results of individual rapid tests when they are evaluated in different studies. To date there are few reports of evaluations that have included more than three rapid tests within the same study (Rodriguez et al., 2002). In this study, however, we have conducted a head-to-head comparison of six influenza rapid tests for their ability to detect influenza A and B on the same clinical specimens and compared these results with laboratory detection methods for influenza.
Section snippets
Clinical specimens
One hundred and seventy-seven respiratory samples (150 nasopharyngeal aspirates; 8 nasal swabs; 8 bronchioalveolar lavages; 6 sputum samples; 5 throat swabs) were obtained from patients with influenza-like illness at the Royal Children's Hospital, Melbourne, Australia between June and October 2006. Patients were aged from 4 days to 64 years old (with 78% of patients being five years old or less), 59% of patients were male and 41% female.
Rapid influenza tests
Six influenza rapid tests—Binax Now Influenza A&B (Binax;
Results
Of the177 clinical specimens obtained, 49 were found to be positive for influenza A antigen by RETCIF; the laboratory based technique which has been used in this evaluation as the ‘gold standard’ for the purposes of rapid test comparisons. An additional specimen was determined to be influenza A positive by real-time RT-PCR (i.e. 50 influenza A positive specimens), while one less specimen was found to be influenza A positive by DIF (48 influenza A positive specimens). Only ten specimens in the
Discussion
Comparisons between the sensitivities of rapid tests evaluated in different studies are inherently difficult given the variability in study designs (patient age, sample type and comparators). As such, studies like this present one, which compared six different rapid influenza tests head-to-head on clinical samples, are of significant value to physicians, general practitioners and others in choosing which influenza rapid test to use. Apart from the Rockeby test, the other five tests demonstrated
Acknowledgements
The authors would like to thank the following for proving rapid test kits for evaluation in this study: Lab Diagnostics, Australia (Binax Now Influenza A&B); Becton Dickinson, Australia (BD Directigen EZ Flu A + B), Denka Seiken, Japan (Quick Ex-Flu), Fujirebio, Japan (Espline Influenza A&B-N), Rockeby, Singapore (Rockeby Influenza A Antigen Test) and Panbio, Australia (Quidel QuickVue Influenza A + B Test).
The WHO Collaborating Centre for Reference and Research on Influenza is supported by the
References (19)
- et al.
‘RETCIF’: a rapid, sensitive method for detection of viruses, applicable for large numbers of clinical samples
J Virol Methods
(2001) - et al.
Comparative analytical sensitivities of six rapid influenza A antigen detection test kits for detection of influenza A subtypes H1N1, H3N2 and H5N1
J Clin Virol
(2007) - et al.
Comparison of Binax NOW and Directigen for rapid detection of influenza A and B
J Clin Virol
(2004) Influenza virus types and subtypes detection by single step single tube multiplex reverse transcription-polymerase chain reaction (RT-PCR) and agarose gel electrophoresis
J Virol Methods
(2002)The global impact of influenza on morbidity and mortality
Vaccine
(1999)- et al.
Comparison of the NOW Influenza A & B, NOW Flu A, NOW Flu B, and Directigen Flu A + B assays, and immunofluorescence with viral culture for the detection of influenza A and B viruses
Diagn Microbiol Infect Dis
(2007) - et al.
A comparison of a rapid test for influenza with laboratory-based diagnosis in a paediatric population
Commun Dis Intell
(2005) - et al.
Impact of the rapid diagnosis of influenza on physician decision-making and patient management in the pediatric emergency department: results of a randomized, prospective, controlled trial
Pediatrics
(2003) - et al.
Comparison of the directigen flu A + B membrane enzyme immunoassay with viral culture for rapid detection of influenza A and B viruses in respiratory specimens
J Clin Microbiol
(2004)